In communications systems, especially those operating in accordance with the GSM (Global System for Mobile communications) or UMTS (Universal Mobile Telecommunications System) standards, data or information is transmitted between a subscriber-side station and a network-side base station over radio interfaces. To set the required emission power in such cases what is known as the Shannon capacity is to be taken into account in each case. The Shannon capacity specifies the maximum volume of data or information that can be sent over a channel when the channel is affected by normal disturbance factors, including noise. The Shannon capacity thus specifies a relationship between emission power and signal-to-noise ratio which may not be exceeded if the receive quality is to be sufficient.
Noting the fact that the subscriber-side stations are mostly mobile stations with a portable energy source, research has long been directed towards minimizing the required signal-to-noise ratio for data transmission in wireless radio communications systems. In addition to the radio communications systems already mentioned, this typically also involves data networks, e.g. in accordance with the HiperLAN2 standard. To allow sending with the lowest possible emission power various methods of error correction have been developed, for example the method known as Forward Error Correction (FEC) referred to as Block FEC, Convolutional FEC, Turbo FEC or Coding FEC. Further error correction methods are what are known as ARQ (ARQ: Automatic Repeat Request) schemes, in which redundant data is transmitted, adaptive modulation methods and so on.
With these type of error correction methods there are especially methods in which a downlink channel is used from the receiver to the original sender, for example to retroactively request a retransmission of incorrect data symbols or, in the case of incremental redundancy, to request more redundancy to be transmitted, as with the ARQ method for example.